This invention relates to indirectly determining the temperature of a fluid. More particularly, it relates to employing the convection heat available in the fluid to produce a substantially uniform temperature in a thermally conductive body and measuring the resultant temperature within the body. In one embodiment, the invention is especially useful for measuring temperatures in the wheelspace area of a gas turbine.
A number of techniques are currently available for directly measuring the temperature of a fluid, such as a gas. However, in some situations, it is either not possible to directly measure the fluid temperature or it is inconvenient to do so. The fluid for which the temperature is to be determined may be flowing at a rapid rate or in a turbulent fashion, and/or the fluid may be corrosive or otherwise damaging to equipment employed for directly measuring the subject temperatures. Furthermore, it may not be possible or convenient to gain access to the fluid in question in order to directly measure its temperature.
One situation in which these factors are important considerations is in determining temperatures within a hot gas turbine For such turbines, a rotatable turbine wheel is typically mounted concentrically in a stationary outer casing. The turbine wheel is usually comprised of a series of blade stages. For each stage, a plurality of airfoil blades are arranged in a row around the outer circumference of the wheel. In operation, a supply of hot gas is directed through passageways in the turbine in such a manner that the gas flows against the turbine blades. The force produced by the gas flow being impinged on the turbine blades causes the turbine wheel to rotate. In this manner, the energy in the gas is converted to rotational movement of the turbine wheel. Besides producing rotational movement of the turbine wheel, this hot gas flow through the turbine also heats a number of the turbine components to elevated temperatures. In some turbine applications, the temperature of components exposed to the hot gas flow can reach levels which exceed their specified temperature capabilities. For those turbines a cooling fluid such as air is often utilized to maintain the temperatures of the exposed components below an acceptable maximum level.
In conventional heavy duty gas turbines, one of the components that is susceptible to overheating caused by hot gas flowing through the turbine is the area of the turbine wheel where airfoil blades are joined to the rotor disc assembly. In order to ensure that this and other areas of the turbine wheel are not subjected to excessively high temperatures during operation of the turbine, the temperature of gas located in an area of the turbine known as a wheelspace is determined and monitored. However, the gas located in this wheelspace area is not easily accessible for direct temperature measurement, and conventional techniques employed for determining this temperature often produce inaccurate results. Furthermore, the temperature sensing means employed is itself susceptible to failure, and is not easily replacable in the designs utilized by prior art wheelspace temperature measuring systems.
Accordingly, it is an object of the present invention to provide a system for indirectly determining the temperature of a fluid in such a manner that the fluid may be isolated from the temperature measuring means employed.
It is also an object of the present invention to provide a temperature determining apparatus for which the accuracy of the results produced is substantially independent of the particular positioning of the temperature sensing means employed, with respect to adjacent portions of the apparatus.
It is a further object of the present invention to provide a system which is especially useful for determining the temperature of gas located in the wheelspace area of a conventional gas turbine.
It is still another object of the present invention to provide an apparatus wherein the temperature sensing means employed is easily replacable.